Originally Posted by
Jashynvald
So, effectively, exp = gil.
Part of the value of the raw materials is the simplicity it has in starting up a craft to be done to gain exp. When the potential for exp the use for it in grinding is used up in the first rounds (log becomes lumber) then the price drops because, to get the same amount of exp, you would have to find other things to combine with it and the subsequent synth after the initial one (like lumber being used for a bow) is more expensive than the original log and entails more hassle with managing different items (sometimes for different DoHs).
In this case, most people don't like what they're going to use for the lumber, instead sell the lumber to make some gil back, and then buy up more logs with disposable income to continue grinding.
So not only is exp = gil, but convenience = gil. When one of those is reduced, then the item's value suffers for it.